Optical lattice clocks with extremely stable frequency are possible when many atoms interrogated simultaneously, but this precision may come at the cost of systematic inaccuracy resulting from atomic interactions. Density-dependent shifts can occur even in a clock that uses fermionic if they subject to inhomogeneous optical excitation. However, sufficiently strong interactions suppress collisional sites containing more than one atom. We demonstrated effectiveness approach strontium by...

The cesium fountain primary frequency standard NIM5 has been developed at the National Institute of Metrology in China. loads atoms an optical molasses from background Cs vapor directly. Atoms are then cooled to a temperature about 2 μK and launched height 81 cm. fringes Ramsey pattern have width 0.98 Hz. operates for more than 300 d year, operating nearly continuously 15 time. By stabilizing 9.19 GHz microwave center central fringe, typical fractional instability 3 × 10−13 (τ/s)−1/2 is...

An optical lattice clock based on 87Sr is built at National Institute of Metrology (NIM) China. The systematic frequency shifts the are evaluated with a total uncertainty 2.3×10−16. To measure its absolute respect to NIM's cesium fountain NIM5, flywheel H-maser NIM5 transferred Sr laboratory through 50-km-long fiber. A fiber comb, phase-locked reference this H-maser, used for measurement. measured be 429228004229873.7(1.4)Hz.

We present a robust, transportable ${\mathrm{Ca}}^{+}$ optical clock, with systematic uncertainty of $1.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}$ limited by the black-body radiation (BBR) field evaluation and an uptime rate $>75%$ over 20-day period. The clock is then installed in air-conditioned car trailer, making it more convenient for applications. Referenced to stationary laboratory geopotential measurements are made total 0.33 m (statistically 0.25 systematically 0.22...

We observe two-body loss of ${}^{3}\phantom{\rule{-0.16em}{0ex}}{P}_{0}$ ${}^{87}$Sr atoms trapped in a one-dimensional optical lattice. measure rate coefficients for atomic samples between 1 and 6 $\ensuremath{\mu}$K that are prepared either single nuclear-spin sublevel or with equal populations two sublevels. The measured temperature preparation dependence agree well calculations reveal distinguishable only slightly enhanced over those indistinguishable atoms. further suppression...

A new absolute distance measurement system is demonstrated in this paper, which based on a dual-wavelength passive mode-locked fiber laser. By controlling the intracavity loss and spectral filtering, cavity by single-wall carbon nanotube saturable absorber able to generate two pulse trains at slightly different repetition rates simultaneously with high mutual coherence. Comparisons commercial interferometers located 80-m large-scale dimensional standard show combined uncertainty of 6 μ m + 1...

Abstract Two 87 Sr optical lattice clocks (OLCs) are being developed and operated at the National Institute of Metrology (NIM), located on different campuses that 40 km apart. In order to compare frequencies these two OLCs, a 58-km noise canceled fiber link is built transfer both 1542-nm laser microwave reference from Changping campus Hepingli campus. commercial frequency combs (OFCs) with adapted single-branch 698/1542 nm outputs coherently unite 698-nm clock lasers laser. The fractional...

We describe recent experimental progress with the JILA Sr optical frequency standard, which has a systematic uncertainty at 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-16</sup> fractional level. An upgraded laser system recently been constructed in our lab may allow standard to reach quantum measurement limit and achieve record levels of stability. To take full advantage these improvements, it will be necessary operate lattice clock...

Abstract We report the 87 Sr optical lattice clock at NIM with a laser referenced to 30 cm ULE cavity. Several improvements, such as atomic temperature and density, frequency stabilization, fiber noise cancellation, etc, have been made since its first evaluation in 2015. Its systematic shifts are carefully evaluated total relative uncertainty of 2.9 × 10 −17 . The measured absolute is 429 228 004 229 873.07(0.13) Hz 3.1 −16 , reference ensemble primary secondary standards published Circular...

We report a robust, compact, and transportable optical clock (TOC-729-2) based on trapped single 40Ca+ ion with systematic uncertainty of 1.1×10−17, which is limited by the black-body radiation shift at room temperature. By comparing it previous (TOC-729-1) similar but completely independent, instability was measured to be better than 1.2×10−14/τ. Benefiting from modular integrated design, this TOC constructed in volume ∼0.33 m3 excluding controlling electronics 19-in. racks. After being...

We report hertz level relative linewidth distributed feedback diode lasers with external optical from a high finesse F-P cavity, and demonstrate the efficient phase noise suppression laser reduction of technique. The is dramatically suppressed throughout measurement frequency range. Especially at Fourier 17 kHz, approximately reference significantly by more than 92 dB. Above this frequency, maintains white plateau as low -124.4 dBc/Hz. laser's FWHM reduced 7 MHz to 4.4 Hz, its instantaneous...

We present a narrow-linewidth diode laser with optical feedback from high-finesse two-mirror nonconfocal cavity. The laser's full-width-at-half-maximum linewidth is reduced to 100 Hz, and its instantaneous 30 Hz in the Lorentzian fitting. To best of our knowledge, it narrowest ever achieved method. phase noise has been significantly by more than 50 dB frequency range 10 kHz. Our experiment demonstrates efficient reduction suppression technique.

NIM-Sr2 optical lattice clock has been developed on the Changping campus of National Institute Metrology (NIM). Considering limitations in NIM-Sr1, several improved parts have designed including a differential pumping stage vacuum system, permanent magnet Zeeman slower, water-cooled anti-Helmholtz coils, an extended viewport for etc. A laser with short-time stability better than 3 × 10 −16 is realized based self-designed 30-cm-long ultra-low expansion cavity. The systematic frequency shift...

Abstract A local time scale can be generated by steering flywheel clocks with state-of-the-art optical lattice clocks. This paper presents our simulations about the influence of clock’s operational strategies and noise characteristics on performance scale. By post-processing measured frequency difference between clock Sr1 hydrogen maser HM50 at National Institute Metrology (NIM), during modified Julian date (MJD) 59029–59059, a 0.68 ns variation referencing to TT(BIPM20) is demonstrated.

We report the observation of resolved atomic interaction sidebands (ISB) in (87)Sr optical clock transition when atoms at microkelvin temperatures are confined a two-dimensional lattice. The ISB manifestation strong interactions that occur between quasi-one-dimensional geometry and disappear confinement is relaxed along one dimension. emergence linked to recently observed suppression collisional frequency shifts. At current temperatures, can be but broad. lower predicted substantially...

We report the experimental realization of a 88Sr magneto-optical trap (MOT) operating at wavelength 461 nm. The MOT is loaded via 32 cm long spin-flip type Zeeman slower which enhances population by factor 22. total laser power available in our experiment about 300 mW. have trapped 1.6 × 108 atoms with 679nm and 707 nm repumping laser. two lasers enhance lifetime factors 11 7, respectively. cloud has temperature 2.3 mK, measured recording time evolution absorption signal.

A clock laser based on a 30-cm-long ultrahigh finesse optical cavity was developed to improve the frequency stability of Sr lattice at National Institute Metrology. Using this probe spin-polarized Sr87 atoms, Rabi transition linewidth 1.8 Hz obtained with 500 ms interrogation time. Two independent digital servos are used alternatively lock S01 (mF=+9/2)→P03 (mF=+9/2) transition. The Allan deviation shows that short-term is better than 3.2×10−16 and averages down followed by 1.8×10−15/τ.

Cold atom clocks have made remarkable progresses in the last two decades and played critical roles precision measurements. Primary Cs fountain frequency standards achieved a total uncertainty of few parts 10 16 , best optical clock has reached type B below −18 . Besides applications metrology, navigation, etc., ultra-stable ultra-accurate atomic also become powerful tools basic scientific investigations. In this paper, we focus on recent developments high-performance cold which can be used...

We present our experiment on magnetic field induced spectroscopy of the 1S0−3P0 transition 88Sr atoms with a 10 Hz linewidth laser. The are cooled by two stage laser cooling. After second narrow line cooling, temperature is reduced to ∼3 μK. then loaded into an 813 nm one-dimensional optical lattice. A homemade 698 and maximum intensity more than 100 W/cm2 used probe in By means ∼1 mT 50 ms pulse ∼6 intensity, Doppler free spectrum 208 obtained.

We report on the magic wavelength measurement of our optical lattice clock based fermion strontium atoms at National Institute Metrology (NIM). A Ti:sapphire solid state laser locked to a reference cavity inside temperature-stabilized vacuum chamber is employed generate lattice. The frequency measured by an erbium fiber comb. trap depth modulated varying power via acousto-optic modulator. obtain shift coefficient this measuring differential transition different depths, and obtained. measure...

We report stable narrow linewidth laser systems based on self-developed Littman configuration external cavity diode lasers (ECDLs). The frequency of the ECDL is stabilized to a high fineness ultralow-expansion glass reference with Pound-Drever-Hall technique. By heterodyne beating two identical systems, we conclude that each reduced lower than 150 Hz and its stability reaches 4.3 × 10-14 at an averaging time 1s, averaged long-term drift less 0.2 Hz/s over 30 h measurement time.

The strontium optical lattice clock has experienced a rapid development since the beginning of 21st century. Its relative frequency uncertainty, on order 10-18, surpassed that cesium fountain clock, current primary standard for time and frequency. This supreme level precision reflects one most advanced measurement capabilities mankind. article reviews progress describes its key components techniques, including high-resolution spectroscopy, close-loop operation, evaluation systematic shifts,...

We report our observation of the spin polarized 1S0 → 3P0 clock transition spectrum in an optical lattice based on fermionic 87Sr. The atoms are trapped and pre-cooled to about 2 μK with two stages laser cooling at 461 nm 689 nm, respectively. Then loaded into formed by interference counter-propagating beams 813 nm. An external cavity diode 698 which is stabilized a high finesse linewidth 5 Hz drift rate less than 0.2 Hz/s, used excite state. π-polarized resolvable mF states obtained...

The NIM4 caesium fountain clock has been operating stably and sub-continually since August 2003. We present our improvements on in 2005–06 the most recent evaluation for its frequency shifts with an uncertainty of 5×10−15. A 203-day comparison between GPS time shows agreement 2×10−14. Finally construction NIM5 transportable is briefly reported.

The frequencies of two 698 nm external cavity diode lasers (ECDLs) are locked separately to independently located ultrahigh finesse optical resonant cavities with the Pound—Drever—Hall technique. linewidth each ECDL is measured be ∼4.6 Hz by their beating and fractional frequency stability below 5 × 10−15 between 1 s 10 averaging time. Another laser injection one cavity-stabilized ECDLs a fixed offset for power amplification while maintaining its characteristics. drift ∼1 Hz/s femtosecond...